1. Field of the Invention
The present invention relates to an active energy beam-curable ink which is curable by being irradiated with, for example, the ultraviolet light and which is preferably applicable to the ink-jet recording system, and an ink jet recording method using the active energy beam-curable ink.
2. Description of the Related Art
Conventionally, an active energy beam-curable composition, which is curable by being irradiated with the active energy beam such as the ultraviolet light or the like, is used for the ink for a printer for screen printing. Such an active energy beam-curable composition is excellent in the curing speed, because any dilution solvent is not used. In particular, such an active energy beam-curable composition is suitable to perform the coating printing, for example, on metal and plastic.
However, the technique for the printer of the ink jet recording system has been improved in recent years. In accordance with this, the demand is gradually increased to perform the coating printing by using the printer of the ink-jet recording system, for example, on the metal and the plastic as well, instead of the printer for the screen printing. In this case, it is also conceived that the active energy beam-curable composition as described above is used as the ink. However, a problem arises such that the viscosity is high, and hence the ink is not stably discharged from the printer head. In order to solve this problem, it is also conceived that the ink is diluted with a solvent to decrease the viscosity. However, a problem arises such that the curing speed is inferior when the ink is diluted with the solvent, which is not preferred in view of the printing characteristic.
On the other hand, Japanese Patent Application Laid-open No. 2002-317139 describes an active energy beam-curable ink containing an alicyclic epoxy resin, an oxetane compound, a cationic polymerization initiator, and a coloring agent. This composition is excellent in the hardness, the curing speed, and the bendability of the cured coating film; and it is affirmed that the composition is usable, for example, for the printing ink.
However, when the active energy beam-curable ink described in Japanese Patent Application Laid-open No. 2002-317139 is used as the ink for the ink-jet recording system, the viscosity is extremely important. If the viscosity is high, the ink is not smoothly jetted from the ink jet nozzle. If the viscosity is low, then the liquid drips from the nozzle to cause the dirt or stain and the leakage thereby. In a case that an active energy beam-curable ink sought for by the present inventors is to be used for the ink-jet, those required include the adhesion or adhesion degree of the cured film of the active energy beam-curable ink with respect to the recording medium and the hardness of the cured film of the active energy beam-curable ink in addition to the viscosity described above. It is necessary to adjust the relationship among them. However, the active energy beam-curable ink described in Japanese Patent Application Laid-open No. 2002-317139 does not necessarily fulfill the three factors as described above.